The present invention relates generally to ventilated enclosures for batteries and other devices that generate potentially explosive or noxious lighter-than-air gases, and more particularly to a passive ventilation system for use in such an enclosure.
It is conventional to employ batteries as a primary or back-up source of electrical power at commercial office buildings and other populated sites, as well as in remote areas to power communications equipment and the like. Typically, batteries used in these environments are housed in insulated, air-tight enclosures that insulate the batteries from ambient temperature variations and the elements of weather. However, because many types of batteries produce hydrogen when overcharged, it is necessary to ventilate the battery enclosure to prevent the build-up of hydrogen beyond an explosive limit.
A known system for use in ventilating hydrogen from a battery enclosure is a passive system which includes a pair of vents that allow hydrogen or any other lighter-than-air gas in the enclosure to vent due to the density difference between the gas and ambient air. One of the vents in the known construction is located at the upper end of the enclosure, and functions as an exhaust from which the low density gas vents from the enclosure, and the second vent permits fresh air to replace the low density gas within the enclosure. Although the second vent is also provided at the top of the enclosure, it includes a horizontal section that extends across the top of the interior space of the enclosure, and a vertical section that depends from the horizontal section toward an opening spaced slightly from the floor of the enclosure.
By providing the horizontal section in the second vent, the conventional construction achieves heat transfer between the gases in the enclosure and the gases in the horizontal section of the second vent, reducing the degree of ventilation of the enclosure that would otherwise occur due to temperature differences between the interior of the enclosure and ambient air. In addition, the down-turned configuration of the conventional construction further reduces temperature-driven ventilation of the enclosure.